SWODY1
SPC AC 190505
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1205 AM CDT FRI MAR 19 2010
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PATTERN SHIFT ALOFT WILL CONTINUE THROUGH PERIOD AS LOW CONTINUES TO
MOVE FARTHER OFF SERN CONUS OVER ATLANTIC. HEIGHTS WILL FALL ACROSS
MUCH OF CENTRAL/SRN ROCKIES AND ADJOINING PLAINS AHEAD OF TWO
PRIMARY SHORTWAVE TROUGHS...
1. INITIALLY OVER SRN NV...AND FCST TO PIVOT SEWD AND EWD ACROSS
NWRN/N-CENTRAL MEX THIS PERIOD.
2. NOW MOVING SSEWD OVER WRN MT...FCST TO CROSS 4-CORNERS REGION
AROUND 20/00Z...DECELERATING AS IT MOVES SEWD OVER REMAINDER NM
DURING ENSUING 12 HOURS.
AT SFC...COLD FRONT IS ANALYZED ATTM FROM SERN CO NEWD ACROSS NWRN
KS AND E-CENTRAL NEB. BY 20/00Z...THIS FRONT SHOULD MOVE SEWD TO
NEAR ORD...COU...BVO...LTS...LBB...ROW...ABQ. BY 20/12Z...FRONT
SHOULD BE INVOF SBN...STL...FSM...DFW...AUS...HDO AND INTO NRN
COAHUILA. FRONTAL-WAVE CYCLONE MAY DEVELOP OVER SERN OK NEAR END OF
PERIOD...AS NM UPPER TROUGH APCHS. DRYLINE...FROM COAHUILA NWD
ACROSS SW TX TO FRONTAL INTERSECTION OVER W-CENTRAL TX...WILL BE
SOMEWHAT DIFFUSE FOR MOST OF PERIOD GIVEN INCOMPLETENESS OF
MOIST-SECTOR AIR MASS MODIFICATION.
...PORTIONS OK...NWRN/W-CENTRAL TX...
BAND OF CONVECTION...INCLUDING WIDELY SCATTERED TO SCATTERED
TSTMS...IS EXPECTED TO FORM INVOF SFC COLD FRONT DURING MID-LATE
AFTERNOON...INCREASING IN COVERAGE INTO AT LEAST EARLY EVENING.
MAIN CONCERN WITH THIS ACTIVITY WILL BE OCCASIONAL HAIL AND GUSTS TO
NEAR SVR LIMITS. LACK OF GREATER PRE-STORM LAPSE RATES
ALOFT...WEAKNESS OF INFLOW-LAYER MOISTURE...AND RESULTING
IMPEDIMENTS TO BUOYANCY...AND MRGL SHEAR PROFILES...COMBINE TO KEEP
SVR POTENTIAL TOO MRGL AND DISORGANIZED FOR CATEGORICAL OUTLOOK
ATTM.
CORRIDOR OF SFC DEW POINTS LOW-MID 50S F -- FRAGMENTED DIURNALLY BY
DIABATIC HEATING/MIXING -- SHOULD RETURN NWD ACROSS N TX AND
PORTIONS OK SE OF COLD FRONT AND E OF DRYLINE. RELATED LOW LEVEL
WAA/MOIST ADVECTION WILL CONTINUE NOCTURNALLY...ALTHOUGH ANTECEDENT
AIR MASS THETAE SHOULD REMAIN SUFFICIENTLY WEAK THAT SIGNIFICANT
INCREASE IN SBCINH WILL OCCUR AHEAD OF FRONT CORRESPONDING TO SFC
DIABATIC COOLING. ACCORDINGLY MODIFIED WRF/ETA-KF SOUNDINGS YIELD
MLCAPE UNDER 750 J/KG OVER NW TX WHERE LAPSE RATES ARE RELATIVELY
MAXIMIZED BUT MOISTURE STILL SPARSE...TO UNDER 500 J/KG OVER CENTRAL
OK WHERE WEAKER LAPSE RATES BUT SLIGHTLY GREATER MOISTURE MAY BE
FOUND. FRONTALLY FORCED CONVECTION -- AIDED BY SFC HEATING --
SHOULD FORM AND SHIFT GENERALLY EWD...WITH SOME SWD BACKBUILDING
TOWARD NRN EDWARDS PLATEAU POSSIBLE.
WITH UPPER TROUGHS STILL LAGGING TO SW AND W OF THIS AREA...ONLY
MODEST HEIGHT-GRADIENT ENHANCEMENT IS EXPECTED...AS WELL AS WEAK
LOW-LEVEL SPEED SHEAR. THIS WILL LIMIT BOTH HODOGRAPH SIZE AND
DEEP-LAYER BULK SHEAR -- E.G. 25-35 KT EFFECTIVE SHEAR ALONG/AHEAD
OF FRONT DURING LATE AFTERNOON/EARLY EVENING. EXPECT SVR
POTENTIAL...THEREFORE...TO BE RATHER SPORADIC...AND TO DIMINISH
AFTER ABOUT 20/03Z AS BOUNDARY LAYER STABILIZES.
TSTMS...HOWEVER....MAY PERSIST INVOF FRONT FOR MUCH OF THE
NIGHT....ROOTED IN REGIME WHERE CONTINUED FRONTAL FORCING IMPINGES
ON ELEVATED WARM-SECTOR LAYER OF INCREASING MOISTURE.
..EDWARDS/STOPPKOTTE.. 03/19/2010
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